Preprint volume - SIBM

Pre-print Volume - Oral presentations
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
of four of the most representative benthic species of the Conero Promontory is
described. This study suggests that, in the North Adriatic Sea, the model describing the
seasonal patterns generally accepted for the Western Mediterranean waters, is modified
according to the peculiar conditions of this area.
Materials and methods – The life cycles of four benthic organisms living along the
Conero Promontory coasts (Ancona) were monthly studied from July 2006 to
November 2009. The area includes natural rocky barriers, scattered rocks and artificial
substrates hosting rich communities mainly composed of mussels, sponges and
cnidarians. In particular we focused on the sponge Tedania anhelans (Lieberkühn,
1859), the scyphozoan Aurelia aurita (L., 1758), the hydrozoan Eudendrium
racemosum (Cavolini, 1785) and the stoloniferan Cornularia cornucopiae (Pallas,
1766). In order to estimate the percentage cover of the sponge, seven squared areas
50×50 cm were considered between 5 and 6 m depth and pictures of the specimens,
taken with an underwater digital camera, were analysed with the Image J software in
order to measure the sponge areas. 75 random replicates of a 20×20 cm frame were
carried out to determine the density variation (in terms of number of colonies m -2 ) of
the hydroid species, while the abundance of stoloniferans and scyphopolyps was
determined with 5 replicates of 10×10 cm frames.
Results – The Conero Promontory presents shallow bottoms, not exceeding 14 m
depth, is continuously invested by currents and is characterized by high sedimentation
rates. The sea temperature in this area reaches the lowest values between January and
February (about 7 °C) while the peak is recorded in August (about 27 °C). Regarding
the seasonal cycle, three pools of species can be recognized: a first group observed all
around the year including several bivalves (mainly Mytilus galloprovincialis and
Ostrea spp.) and massive sponges (Chondrosia reniformis, Ircinia variabilis, Aplysina
aerophoba); a second group including organisms occurring only during the winter
period (for example the hydroids Ectopleura crocea, Obelia dichotoma and Coryne sp.
and the bryozoan Bugula sp.); the third and most important group is composed by
spring-summer species (the sponges Oscarella lobularis and T. anhelans, the hydroids
E. racemosum, Halocordyle disticha and Coryne eximia and the stoloniferan C.
cornucopiae). A. aurita polyps are eurythermal, able to adapt to a wide range of
environments, and at Conero Promontory they are observed throughout the year; while
low temperatures trigger the strobilation in winter, there is a positive relation between
polyp number and temperature increase in summer.
Concerning the organisms studied in detail, T. anhelans (Fig. 1A) shows a marked
seasonal cycle reaching maximum values of percentage covering in summer (20% ±3.5
SE) and almost disappearing in autumn-winter. The species intensively reproduces
asexually from April to August giving rise to simple or ramified propagules that detach
from the sponge body. A. aurita (Fig. 1B) reaches density values higher than 45 polyps
cm -2 in summer then decreases showing the minima between February and April (12-20
polyps cm -2 ) (Di Camillo et al., 2010). E. racemosum (Fig. 1C) shows low densities
during autumn (15-160 colonies m -2 ) then falls down to zero during winter when
hydrorhizae act as resting stages. The colony density quickly increases in spring (22-
200 colonies m -2 ) and reaches the maximum value in August (with an average of
almost 400 colonies m -2 ). The reproduction also occurs in the warm season. C.
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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